Precise and accurate active device under test (DUT) test site temperature measurement reduces errors when using a temperature controlled thermal strip chuck. The test site temperature will still change by some small amount, however the temperature measurement device will catch and react to these small temperature changes for a further reduction of errors caused by temperature changes during measurement and calibration (trimming) of the DUT. Tightly controlled temperature improves calibration accuracy and improves repeatability of the DUT operating characteristics.